Translation of rostfrei

I hope you could understand my last letter to you. You see, when I write in Spanish I am not very confident. I always question myself and each and every sentence takes about fifteen minutes.
As promised, I am sending you in the attachment a (very) little overview of some applications we created on Vocabulix. Please send me also some infos about your activities. When would be the best time to talk?
At the moment we want to keep Vocabulix free. However, we recently added a donation button at the end of each lesson (by Paypal). You may donate 10$ after completing your next lesson. That will do.